PPG and Dupont codes are available in this Stovebolt.com Tech Tip. At the bottom of the Tech Tip are instructions on how to find out from PPG the modern offset code and paint name.

If you do not have a PPG jobber near you (from which to buy the paint), you might/should be able to use the PPG offset name and year to find a match in another line of paints.

1947-52 Mariner Blue
Dupont: 63203
PPG: 10419

The 1953 and later Mariner Blue is a different shade/formula (PPG can deal with this but Dupont shows the same code for all years).

Tim